Malignant tumors rank first among death causes in Japan. Thus various treatments including chemotherapeutic, surgical and radiotherapeutic ones have been remarkably advanced in order to overcome this disease. Recently progress in chemotherapy has made it possible to overcome specific cancers such as juvenile leukemia little by little. In the case of solid tumors, however, surgical treatments are still mainly effected and there are few cases where this disease is healed exclusively by chemotherapy only. Many chemotherapeutic agents would exert only limited growth suppressing effects on solid tumors. Furthermore, various side effects accompanying chemotherapy substantially restrict these treatments.
Xanthocillin X monomethyl ether, which is the starting material for the synthesis of the compound of the present invention, is a known substance produced by Dichotomomyces albus belonging to Fungi Imperfecti (cf. K. Ando et al., J. Antibiotics, 21, 582-586 (1968)). Xanthocillin X monomethyl ether was purified and isolated as an antiviral substance. Furthermore, studies on the antitumor activity of this compound revealed that it would suppress the proliferation of Ehrich ascites tumor but the cancer cells would proliferate again immediately after stopping the administration of this compound. These results suggested that xanthocillin X monomethyl ether was not practically available as an antitumor agent. Individually, it was clarified that this compound would inhibit the biosynthesis of prostaglandin or thromboxane, namely, the conversion of arachidonic acid into prostaglandin H.sub.2 (cf. N. Kitahara et al., J. Antibiotics, 34, 1556-1561 (1981)).